Jupiter's icy moon Europa is pockmarked by mysterious domes and depressions that now seem to be areas where liquid water once appeared close to the surface. Thera Macula is one such region of likely active chaos production above a large liquid water lake in the icy shell of Europa. Color indicates topographic heights relative to background terrain. Purples and reds indicate the highest terrain.

Europa is thought to harbour a saltwater ocean, sandwiched between a 20-kilometre-thick layer of surface ice and a rocky core below. For clues as to what might be happening there, Britney Schmidt of the University of Texas, Austin, and colleagues looked at studies of subglacial volcanoes and ice shelves on Earth. They concluded that ice rising from the bottom of Europa's surface layer created its 300-metre-high "chaos terrains".

In a significant finding in the search for life beyond Earth, the science teams at The University of Texas and elsewhere have discovered what appears to be a body of liquid water the volume of the North American Great Lakes locked inside the icy shell of Jupiter’s moon Europa. The water could represent a potential habitat for life, and many more such lakes might exist throughout the shallow regions of Europa’s shell, lead author Britney Schmidt, a postdoctoral fellow at the university’s Institute for Geophysics, writes in the journal Nature.

Further increasing the potential for life, the newly discovered lake is covered by floating ice shelves that seem to be collapsing, providing a mechanism for transferring nutrients and energy between the surface and a vast ocean already inferred to exist below the thick ice shell.

“This new understanding of processes on Europa would not have been possible without the foundation of the last 20 years of observations over Earth’s ice sheets and floating ice shelves,” said Don Blankenship, a co-author and senior research scientist at the Institute for Geophysics, where he leads airborne radar studies of Earth’s ice sheets.

The large dark spot on Europa called Thera Macula above could result from warm ice rising beneath it, Schmidt told New Scientist. "We are probably witnessing active chaos formation."